Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$188.68	6.442%	$200.8348	$200.83	$200.85	$200.80
Purchase #2	$91.81	10.142%	$101.1214	$101.12	$101.10	$101.10
Purchase #3	$15.54	9.373%	$16.9966	$17.00	$17.00	$17.00
Purchase #4	$34.93	7.480%	$37.5428	$37.54	$37.55	$37.50
Purchase #5	$30.64	3.223%	$31.6275	$31.63	$31.65	$31.60
Purchase #6	$122.93	6.221%	$130.5775	$130.58	$130.60	$130.60
Purchase #7	$41.31	10.216%	$45.5302	$45.53	$45.55	$45.50
7 purchase totals =	$525.84		$564.2308	$564.23	$564.30	$564.10